Printing System, Printing Method, and Medium Storing Control Program for the Printing System

ABSTRACT

Heretofore there has been a case where a monochromatic image having a sufficient power of expression cannot be printed because of a narrow selection range of saturation. According to the present invention, in a predetermined print head, there is adopted a construction wherein the gradation characteristic of a color region capable of being color-reproduced is enhanced while narrowing the color region with use of a cyan color ink of a low saturation, a magenta color ink of a low saturation, a yellow color ink of a high saturation, and a black color ink, and color reproduction is performed. The color tone of the printed monochromatic image can be adjusted minutely with respect to the color components of cyan and magenta. On the other hand, the color region capable of being color-reproduced is wide substantially in the direction of yellow. Therefore, it is possible to ensure a sufficient selection range of saturation and print a monochromatic image of a high image quality having a sufficient power of expression.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 10/973,287 filedOct. 27, 2004, which in turn is a continuation of U.S. application Ser.No. 10/209,663 filed Aug. 1, 2002; the disclosures of both Applicationsare incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a printing system, a printing method, acontrol program for the printing system, and a medium which stores thecontrol program for the printing system.

2. Description of the Prior Art

According to the prior art, when a monochromatic image of a high qualityhaving what is called sepia color or warm color is printed using aprinter, color reproduction is performed using such chromatic color inksas a cyan color ink, a magenta color ink, and a yellow color ink, inaddition to a black color ink. By the way, a black color ink usuallycontains carbon black, and the darkness of a black color ink depends onthe quantity of the carbon black contained. Hereinafter a plurality ofblack color ink with different darkness are used, and the term of ablack color ink is sometimes used as a general term for several blackcolor inks with different darkness. In this case, for adjusting thecolor tone using chromatic color inks minutely, there are separatelyprovided a cyan color ink, a magenta color ink and a yellow color ink,which are low in saturation, and printing of a monochromatic image isconducted using those inks.

But the aforesaid prior art has involved the following problems.

Due to a narrow selection range of saturation there sometimes has been acase where a monochromatic image having a sufficient power of expressioncannot be printed. Further, in the case of a printer that can print incolors, it is necessary to separately provide special color inks.

SUMMARY OF THE INVENTION

The present invention has been accomplished in view of theabove-mentioned problems and it is an object of the invention to providea printing system and printing method capable of ensuring a sufficientselection range of saturation and printing a monochromatic image of ahigh image quality having a sufficient power of expression, as well as acontrol program for the printing system and a medium which stores thecontrol program for the printing system.

For achieving the above-mentioned object, the present invention adopts aconstruction wherein, in a predetermined print head, the gradationcharacteristic of a color region capable of being color-reproduced isenhanced while narrowing the color region with use of a cyan color inkof a low saturation, a magenta color ink of a low saturation, a yellowcolor ink of a high saturation, and a black color ink, and colorreproduction is performed.

In one aspect of the present invention which adopts the aboveconstruction, the color-reproducible color region is narrowedsubstantially in the directions of cyan and magenta by the cyan andmagenta color inks low in saturation. As a result, the color tone of themonochromatic image printed can be adjusted minutely because thegradation characteristic is enhanced as to cyan and magenta colorcomponents. With the yellow color ink of a high saturation, thecolor-reproducible color region is wide substantially in the directionof yellow. When looking at the monochromatic image, the human eyes sensethe yellow component as a relatively small component in comparison withcyan and magenta components, so even if there is used a yellow color inkof a high saturation, it is possible to develop color tone of a finetexture in appearance. That is, while developing a color tone of a finetexture in appearance, it is possible to ensure a sufficient selectionrange of saturation of the printed monochromatic image and obtain asufficient power of expression.

Thus, according to the present invention, it is possible to provide aprinting system and printing method capable of ensuring a sufficientselection range of saturation and printing a monochromatic image of ahigh image quality having a sufficient power of expression, as well as acontrol program for the printing system and a medium which stores thecontrol program for the printing system.

In another aspect of the present invention, as an example of the abovevarious color inks, the foregoing yellow color ink of a high saturationmay be constituted by an ink of a high saturation and a high density,the foregoing cyan color ink of a low saturation may be constituted byan ink low in both saturation and density, and the foregoing magentacolor ink may be constituted by an ink low in both saturation anddensity. That is, the color-reproducible color region is narrowedsubstantially in the directions of cyan and magenta by the cyan andmagenta inks low in both saturation and density. Substantially in thedirection of yellow the same color region is widened by the yellow colorink high in both saturation and density. Consequently, with these colorinks, it is possible to ensure a sufficient selection range ofsaturation of a monochromatic image printed and obtain a sufficientpower of expression while developing a color tone of a fine texture inappearance.

Moreover, this can provide examples of various color inks.

In the case of a printing system that can make printing in colors usingsix colors of inks, it is not necessary to provide special color inksseparately because there are included cyan and magenta color inks low inboth saturation and density.

By making both cyan and magenta color inks low in density, thebrightness of the cyan color ink and that of the magenta color inkbecome close to that of yellow color ink, so that the gap in brightnesscaused by a difference in hue becomes small and it is possible to printa monochromatic image of a high image quality.

As examples of the Black color ink are included not only black color inkwith hue not imparted thereto but also black color ink with hue impartedthereto. As examples of the cyan color ink are included mixtures of acyan color ink as a main component with other kinds of color inks. Thisis also true of magenta and yellow color inks.

The printing system according to the present invention maybe composed ofa printer and a computer connected to the printer, or may be constitutedby a printer alone. Various system configurations can be adopted.

Ina further aspect of the present invention, as an example of a printingsystem that can effect both monochromatic image printing and colorprinting, there may be adopted a construction wherein, in colorprinting, color reproduction is performed using a cyan color ink high inboth saturation and density and a magenta color ink high in bothsaturation and density together with the aforesaid various color inks,while in monochromatic image printing, such cyan and magenta color inkshigh in both saturation and density are not used. In case ofincorporating a small amount of cyan and magenta into a monochromaticimage, there sometimes occurs what is called a color twist phenomenonsuch that with a color ink high in both saturation and density there isdeveloped an unintended hue because of a low dot density. However,according to the construction in question, such a color twist phenomenondoes not occur because cyan and magenta color inks high in bothsaturation and density are not used in monochromatic image printing.

According to this construction, moreover, there does not appear anyunintended hue and it is possible to print a monochromatic image of ahigh image quality.

For changing inks to be used in accordance with the type of printing,color conversion tables for conversion from printing data to data fordriving a print head may be provided correspondingly to printing typesand may be switched from one to another according to the type ofprinting.

In a still further aspect of the present invention, an example ofconstruction of the Black color ink comprises plural Black color inksdifferent in density, and printing may be conducted using any or acombination of such Black color inks. That is, not only an appropriateBlack color ink can be selected according to the brightness of image butalso it is possible to diminish the gap in brightness at the time ofreplacing various chromatic color inks with Black color inks.

This allows the image quality of a monochromatic image printed to beimproved because not only an appropriate Black color ink can be selectedaccording to the brightness of image but also it is possible to diminishthe gap in brightness at the time of replacing various chromatic colorinks with Black color inks.

In a still further aspect of the present invention, as an example ofconstruction using plural Black color inks different in density, theabove Black color inks are a black color ink and a light black color inklower in density than the black color ink. The light blank color ink maybe provided so that it can be replaced with one or both of cyan andmagenta color inks high in both saturation and density. That is, even ifthe number of ink cartridges which can be loaded to the printing systemis limited, both printing of a monochromatic image of a high quality andcolor printing can be done in one and same printing system. For example,in the case of a printing system loaded with six kinds of color inks andable to make coloring printing, all that is required is to provide twokinds of light black color inks different in density and load then intoink cartridges in place of cyan and magenta color inks low in bothsaturation and density used in color printing. It goes without sayingthat these light black color inks, as well as cyan and magenta colorinks low in saturation and density, may be loaded into ink cartridgesand both printing of a monochromatic image of a high image quality andcolor printing may be done in one and same printing system.

This can, even if the number of ink cartridges is limited, effect bothprinting of a monochromatic image of a high image quality and colorprinting in one and same printing system.

There sometimes occurs a case where various color inks are to be usedwhile taking into account the running cost of a printing system used. Inview of this point, according to a further aspect of the presentinvention, there is provided a ratio setting acquiring means foracquiring the setting of a ratio between such plural Black color inks asreferred to above and other color inks and printing is performed inaccordance with the setting of the ratio acquired. If there are usedmany chromatic color inks, the running cost is apt to increase althoughthe image quality will be improved. With the ratio setting acquiringmeans, it is possible to set the ratio between plural Black color inksand other color inks, with the result that it becomes possible to selectaccording to preference whether the printing to be performed is aprinting with importance attached to image quality or is a printing withimportance attached to running cost.

In this way it is possible to set an appropriate ratio between pluralBlack color inks and other color inks and improve the convenience.

In a still further aspect of the present invention, as an example of asuitable construction for performing both monochromatic image printingand color printing in one and same printing system, there maybe adopteda construction wherein there is provided a print type acquiring meansfor acquiring a print type out of a monochromatic image printing typeand a color printing type, and printing is performed in accordance withthe print type acquired. Thus, with the print type acquiring means, itis possible to set whether the printing to be performed is monochromaticimage printing or color printing, whereby the convenience is improved.It is optional whether the print type acquiring means should use anoperation input or an application program to acquire a print type.

In this way it is possible to set whether the printing to be performedis monochromatic image printing or color printing and hence possible toimprove the convenience.

In the present invention, while narrowing a color-reproducible colorregion by using a yellow color ink of a high saturation, the gradationcharacteristic in the said color region is enhanced and printing of amonochromatic image of a high image quality is performed. In thisconnection, according to a further aspect of the present invention thereis provided a printing system wherein, in printing a monochromaticimage, there are used an achromatic color ink and a chromatic color inkof a low saturation which narrows a printable color region to a lowersaturation side than in color printing, thereby effecting colorreproduction in a narrower color region than in color printing. In thisprinting system, a yellow color ink high in saturation is used togetherwith the above achromatic color ink and chromatic color ink of a lowsaturation, and printing of a monochromatic image is performed withoutnarrowing the above color region from the time of color printingsubstantially in the direction of yellow.

That is, by using an achromatic color ink, a chromatic color ink of alow saturation, and a yellow color ink of a high saturation, the colorregion is not narrowed from the time of color printing substantially inthe direction of yellow, but is narrowed from the time of color printingsubstantially in the other directions than the direction of yellow. Inother words, by using a yellow color ink of a high saturation, thecolor-reproducible color region becomes wide substantially in thedirection of yellow. As noted earlier, the human eyes sense yellowcomponent relatively lower than cyan and magenta components, so even ifthere is used a yellow color ink of a high saturation at the time ofprinting a monochromatic image, it is possible to develop a color toneof a fine texture in appearance. Consequently, it becomes possible toensure a sufficient selection range of saturation of the monochromaticimage printed and obtain a sufficient power of expression. Besides, withuse of achromatic color ink of a low saturation, the brightness of thechromatic color ink approaches the brightness of the yellow color ink ofa high saturation, so that the gap in brightness caused by thedifference in hue becomes smaller.

The achromatic color ink may be a black or gray color ink or may be evena black color ink with hue imparted thereto. The chromatic color ink ofa low saturation may be a light cyan color ink, a light magenta colorink, or a color ink intermediate between light cyan and light magenta.

As noted above, the object of application of the technique whichenhances the gradation characteristic in a color-reproducible regionwhile narrowing the same region and which performs color reproduction inthis state is not always limited to a substantial system, but it is amatter of course that a predetermined processing procedure for the colorreproduction underlies the invention. Thus, the present invention isalso applicable as a method and it goes without saying that the abovesystem configuration can be made corresponding to the method.

In carrying out the present invention there sometimes occurs a casewhere a predetermined program is allowed to be executed by a computer ina printing system wherein color reproduction is made with apredetermined print head using plural kinds of color inks. It goeswithout saying that the above system configuration can be madecorresponding to the said control program.

Further, in carrying out the present invention there sometimes is a casewhere a medium which stores the above control program is in distributionand the control program is allowed to be executed by a computer. It goeswithout saying that the foregoing system configuration can be madecorresponding to the above medium storing the control program.

A recording medium capable of being read by a computer may be a magneticrecording medium or a magneto-optic recording medium. This is completelytrue of any of recording mediums to be developed in future. The idea ofthe present invention is also applicable completely equally to the casewhere a part is software and a part is implemented by hardware. Furtherincluded is a mode in which a part is recorded on a recording medium andis read as necessary. There is no room for doubt that this is also trueof such duplicating stages as primary and secondary duplicates.

Other and further objects, features and advantages of the invention willappear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a schematic construction of a printingsystem according to an embodiment of the present invention;

FIG. 2 is a block diagram showing a block configuration of a printertogether with a personal computer;

FIG. 3 is a diagram showing an arrangement of nozzles in a print head;

FIG. 4 is a block diagram showing an execution environment of a printerdriver;

FIG. 5 is a diagram showing schematically changes of data which occurwhen printing data prepared by APL are converted to printing jobs;

FIG. 6 is a diagram showing changes in brightness relative to inkimplantation quantities which occur when color inks are ejected eachindividually;

FIG. 7 is a diagram in which a color region capable of beingcolor-reproduced by plural color inks is shown schematically by beingprojected on an a*L* plane in an L*a*b* space;

FIG. 8 is a diagram in which a color region capable of beingcolor-reproduced by plural color inks is shown schematically by beingprojected on an a*b* plane in an L*a*b* space;

FIG. 9 is a schematic diagram in which dots formed are compared betweenthe use of C and M high in both saturation and density and the use of cand m low in both saturation and density;

FIG. 10 is a diagram in which the amounts of color inks used relative tothe brightness of a monochromatic image are shown in terms of gradationvalues;

FIG. 11 is a diagram in which the amounts of color inks used relative tothe brightness of a monochromatic image are shown in terms of gradationvalues;

FIG. 12 is a flowchart showing an outline of processings executed by apersonal computer;

FIG. 13 is a flowchart showing an outline of processings executed by thepersonal computer;

FIG. 14 is a flowchart showing an outline of processings executed by thepersonal computer; and

FIG. 15 is a diagram showing an example of a display on a print typesetting screen.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described hereinunder inaccordance with the following procedure:

-   -   (1) Construction of a printing system    -   (2) Changes of data in conversion from printing data to printing        jobs    -   (3) Color-reproducible color region in monochromatic image        printing    -   (4) Operation of the printing system    -   (5) Modifications

(1) Construction of a Printing System

FIG. 1 illustrates a schematic construction of a printing system 100according to an embodiment of the present invention. A blockconfiguration of a person computer (PC) 10 is also shown in the samefigure.

The printing system 100 of this embodiment comprises a personal computer10 and a printer 20 which can make color printing. Therefore, theprinting system 100 can perform not only printing of a monochromaticimage but also color printing. The monochromatic image means an imagehaving a substantially unitary hue. It is not limited to an imageprinted using a single color ink, but it can be printed using pluralkinds of color inks at approximate equal proportions.

The personal computer 10 is provided with a CPU 11 which serves as thenucleus in arithmetic processing. The CPU 11 controls the whole of thepersonal computer 10 through a system bus 10 a. ROM 12, RAM 13, harddisc drive 14, CD-ROM drive 15, input interface (input I/F) 16, CRTinterface (CRT I/F) 17, communication interface (communication I/F) 18,and printer interface (printer I/F) 19 are connected to the system bus10 a.

The personal computer 10 used in this embodiment is what is called adesk top type personal computer and is described in a simplified stateof its configuration. Of course, a computer having a general computerconfiguration is employable as the personal computer 10. For example, anotebook type or a mobile computer will do. The computer applicable tothe printing system of the present invention is not limited to thepersonal computer.

In a hard disc 14 a connected to the hard disc drive 14 there are storedan operating system (OS) as software and application programs (APL)which can generate document information and image information. Thesesoftwares, when to be executed, are transferred as necessary to the RAM13 by CPU 11. Then, the CPU 11 executes various programs while makingaccess as necessary to the RAM 13 as a temporary work area.

To the input I/F 16 are connected a keyboard 16 a and a mouse 16 b asoperating input devices and also connected are a scanner and a digitalcamera (neither shown). Therefore, it is possible to read an image fromthe scanner or the digital camera and effect printing of a monochromaticimage.

A display 17 a is connected to the CRT I/F 17. Further, The printer 20is connected to the printer I/F 19 through a parallel interface cable.Of course, it is not always necessary that the interface for connectionwith the printer 20 be limited to the parallel interface. Variousconnection modes may be adopted, including serial interface, SCSI, andUSB connections. Any other connection modes to be developed in futureare also employable.

Although the above softwares are stored in the hardware 14 a, therecording medium which can store the softwares is not limited to thehard disc. For example, it may be a CD-ROM or a flexible disc. Thesoftwares stored in any of these recording mediums are read through theCD-ROM drive 15 or a flexible disc drive (not shown) and are installedin the hard disc 14 a, then are read onto the RAM 13 by CPU 11, which inturn executes various processings. As to the recording medium, nolimitation is made to those referred to above, but there may be used amagneto-optic disc or a non-volatile memory as a semiconductor device.Further, the communication I/F 18 such as a modem connected to thesystem bus 10 a may be connected to the Internet and access may be madeto a server capable of storing various programs, allowing softwares tobe down-loaded.

The printer 20 used in this embodiment is an ink jet printer and employsa total of six color inks in color printing, which are a cyan color ink(C) high in both saturation and density, a magenta color ink (M) high inboth saturation and density, a yellow color ink (Y) high in bothsaturation and density, a cyan color ink (c) low in both saturation anddensity and called light cyan, a magenta color ink (m) low in bothsaturation and density and called light magenta, and a black color ink(k) which is one of a black color ink in general meaning. On the otherhand, in monochromatic image printing, two kinds of light black colorinks (k1, k2), which are also one of a black color ink in generalmeaning, and they are low in density, are used instead of high-densitycyan and magenta.

In the following description and also in the drawings the colors of inkswill be described merely as C, M, Y, c, m, K, k1, and k2. The color inksC, M, Y, c, and m are chromatic color inks, while the color inks K, k1,and k2 are achromatic inks. k1 is higher in brightness than K, and k2 isstill higher in brightness than k1.

In printing a monochromatic image, if dots of a magenta color ink or ayellow color ink are mixed in dots of a black color ink, it is possibleto color-reproduce a monochromatic image of what is called sepia or warmcolor. Likewise, if dots of a cyan or magenta color ink are mixed indots of a black color ink, it is possible to color-reproduce amonochromatic image of what is called cool color. In this embodiment,dots of the color inks c, m, and Y are mixed in dots of the color inksK, k1, and k2. As a result, it becomes possible to create a uniqueatmosphere such as an atmosphere suggestive of an old photograph.

FIG. 2 shows a block construction of the printer 20 together with thepersonal computer 10. A bus 20 a is provided in the interior of theprinter 20, and CPU 21, ROM 22, RAM 23, ASIC 24, control IC 25,communication I/O 26, and interface (I/F) 27 for the transmission ofimage data and drive signals, are connected to the bus 20 a. The CPU 21controls various portions in accordance with programs stored in the ROM22 while utilizing RAM 23 as a work area.

ASIC 24 is an IC customized for driving a print head (not shown) and itperforms processings for driving the print head while transmitting andreceiving predetermined signals to and from the CPU 21. Further, theASIC 24 outputs applied voltage data for a head driver 29.

The head driver 29 is a circuit which comprises a dedicated IC, adriving transistor, and a heat sink. In accordance with the appliedvoltage data inputted from ASIC 24 the head driver 29 generates anapplied voltage pattern for piezoelectric elements incorporated in theprint head. The print head is connected cartridge holders 28 throughtubes provided color ink by color ink, the cartridge holders 28 beingloaded with six ink cartridges 28 a to 28 f respectively and suppliedwith color inks. Piezoelectric elements are actuated within ink chamberscommunicating between the tubes and orifices, whereby inks are ejected.

FIG. 3 shows an arrangement of the nozzles. On an ink ejecting surfaceof a print head 30 there are formed six nozzle columns 31 to 36 forejecting six kinds of color inks respectively, the nozzle columns 31 to36 being arranged side by side in a horizontal scanning direction. Ineach of the nozzle columns 31 to 36, plural nozzles (say, 48 nozzles)are arranged linearly at predetermined intervals in a vertical scanningdirection.

The six ink cartridges 28 a to 28 f are filled with six different kindsof color inks respectively. In color printing, the ink cartridges K, C,M, Y, c, and m are loaded in the order of 28 a to 28 f. On the otherhand, in monochromatic image printing, the ink cartridges K, k1, k2, Y,c, and m are loaded in the order of 28 a to 28 f. That is, the inkcartridges C and k1 can be loaded replaceably to the same cartridgeholder 28, and the ink cartridges M and k2 can be loaded replaceably tothe same cartridge holder 28.

Cartridge memories, which are non-volatile memories, are mounted on theink cartridges 28 a to 28 f respectively to store the colors andresidual amounts of loaded inks. When the ink cartridges are loaded tothe cartridge holders 28, the cartridge memories are electricallyconnected to the control IC 25. The cartridge holders 28 are eachprovided with an ink supply needle, which comes into contact with an inksupply port (not shown) formed in each ink cartridge loaded to form anink supply path. Through this ink supply path the color ink in the inkcartridge is fed to the print head 30 through the associated tube. Incolor printing, the color inks K, C, M, Y, c, and m are fed in the orderof nozzle columns 31 to 36, while in monochromatic image printing thecolor inks K, k1, k2, Y, c, and m are fed in the order to nozzle columns31 to 36.

The control IC 25 is an IC mounted for controlling the plural cartridgememories. The CPU 21 transmits and receives predetermined signals to andfrom the control IC 25, reads out information such as ink colors andresidual amounts of inks stored in the cartridge memories, and updatesinformation on residual amounts of inks. Further, the CPU 21 detects aloaded state of each of the ink cartridges 28 a to 28 f and outputs asignal indicative of removal or loading.

The communication I/O 26 is connected to the printer I/F 19 in thepersonal computer 10 and the printer 20 receives a printing jobcomprising data converted to K, C, M, Y, etc. and a page describinglanguage, provided from the personal computer 10 through thecommunication I/O 26. Upon receipt of various requests from the personalcomputer 10, the communication I/O outputs color ink informationindicative of colors and loaded states of inks provided from the controlIC 25 to the personal computer 10.

A carriage mechanism 27 a and a paper feed mechanism 27 b are connectedto the I/F 27. The paper feed mechanism 27 b, which comprises a paperfeed motor and a paper feed roller, functions to feed aprinting/recording medium such as printing paper successively andperforms a vertical scanning. The carriage mechanism 27 a comprises acarriage for mounting the print head 30 thereon and a carriage motor forcausing the carriage to travel through a timing belt or the like. Thecarriage mechanism 27 a causes the print head 30 to perform a horizontalscanning. In the print head 30 provided with plural nozzles in thevertical scanning direction, piezoelectric elements are actuated on thebasis of head data constituted by a bit string and in accordance with adrive signal outputted from the head driver 29, causing ink droplets tobe ejected in dot unit from the nozzles.

In the personal computer 10, BIOS (basic input output system) isexecuted on the basis of the above hardware, and OS and APL are executedin an overlying layer. Basically, OS accesses the hardware through BIOSor directly, while APL transmits and receives data to and from thehardware through OS.

Various drivers for controlling the hardware are incorporated in OS andexecute various controls as part of OS. The drivers include a displaydriver for controlling the CRT I/F 17 and a printer driver forcontrolling the printer I/F 19.

FIG. 4 illustrates a execution environment of the above printer driverin terms of a block diagram. The printer driver is operated at the timeof executing the printing function of APL and can make two-waycommunications with the printer 20 through the printer I/F 19. Theprinter driver receives printing data from APL through OS, then preparesa printing job, and transmits the printing job to the printer 20.Further, the printer driver sends to the printer 20 a request forinformation indicative of ink colors and loaded states of ink cartridgesand receives corresponding information from the printer 20, through theprinter I/F 19.

In the OS are incorporated GDI (Graphics Device Interface) whichimplements a graphic user interface function between APL and OS withrespect to graphics such as graphic image information and documentinformation, and a port driver which stores printing data received fromAPL as an intermediate file to a predetermined area of the hard disc 14a and which generates a printing job by performing a predeterminedprocessing for the intermediate file and transmits it to the printer 20.

The printer driver has a printing data acquiring module m1, anintermediate file generating module m2, a printing job generating modulem3, and a print setting acquiring module m4, and can generate a printingjob simultaneously with executing a predetermined function under controlof a function control module (not shown).

The printing data acquiring module ml acquires printing Data generatedby APL from GDI. The intermediate file generating module m2 generates anintermediate file from the printing data which the printing dataacquiring module ml has acquired, and then stores it in the hard disc 14a temporarily. The printing job generating module m3 acquires theintermediate file as necessary, executes an image processing forconverting data based on RGB into color data based on K, C, M, Y, etc.,generates a printing job, and outputs it to the printer 20 through theport driver. At this time, the printing job is generated on the basis ofvarious printing parameters acquired by the print setting acquiringmodule m4.

(2) Changes of Data in Conversion From Printing Data to Printing Jobs

At the time of conversion from data based on RGB to the above color datathere is used a color conversion table called LUT (look-up table). Inthis embodiment, in color printing, there is used LUT wherein data basedon RGB are correlated with six kinds of color data K, C, M, Y, c, m,while in monochromatic image printing there is used LUT wherein databased on RGB are correlated with six kinds of color data K, k1, k2, Y,c, m.

FIG. 5 schematically shows changes of data in conversion from printingdata prepared by APL to printing jobs.

Printing data D1 generated by APL is a printing command for generating aprinting job in accordance with a predetermined rule. The printing dataD1 is delivered o the printer driver through GDI by the printing dataacquiring module m1 and is rewritten into an intermediate language bythe intermediate file generating module m2, which language is stored asan intermediate file D2 into the hard disc 14 a temporarily. Theintermediate file D2 is read to RAM 13 and is converted to bit map dataof 256 gray scales with eight bits allocated for each of RGB on thebasis of the intermediate language contained in the interior, to giveRGB bit map data D3 and D4. Of course, the gradation of RGB bit map dataD3 and D4 is not limited to 256 gray scales, but various other valuesmay be adopted.

The printer driver used in this embodiment has a function of imparting ahue to an achromatic image so as to give a desired tone in monochromaticimage printing. In monochromatic image printing, therefore, theintermediate file D2 is once converted to achromatic bit map data, thena hue which is acquired by a setting process to be described later isimparted to the data and conversion is made into RGB bit map data D4.

Of course, printing data of a monochromatic image with such a hue asaffords a desired tone imparted thereto may be prepared in APL. In thiscase, the printer driver is not required to have the function ofimparting hue to the achromatic image, but can prepare RGB bit map datadirectly after preparing an intermediate file from printing dataprepared by APL and can thereby prepare a printing job for monochromaticimage printing.

In accordance with LUTs which correspond to the print type acquired bythe print setting acquiring module m4, etc. the RGB bit map data D3 andD4 are converted respectively to color data D5 and D6 of 256 gray scaleswith eight bits allocated to each color ink. Also as to the gradation ofthe color data D5 and DG, various other values than 256 gray scales maybe adopted. In the figure, LUT used in color printing is described asLUT1, while LUTs used in monochromatic image printing are described asLUT2 (priority given to high image quality) and LUT3 (priority given torunning cost). LUT1 is a table wherein RGB bit map data are correlatedwith color data K, C, M, Y, c, m, while LUT2 and LUT3 are tables whereinRGB bit map data are correlated with color data K, C, M, Y, c, m. Thesetables LUT1 to LUT3 are determined according to color characteristics ofthe color inks.

The color data D5 and D6 are binarized by an error diffusion method andare converted to printing jobs D7 and D8 for output to the printer 20.Of course, the method for binarizing the color data D5 and D6 is notlimited to the error diffusion method. There may be adopted anotherbinarizing method such as the dither method. It is the modules m3 and m4that causes the personal computer 10 to implement the processing ofpreparing the printing jobs D7 and D8 from the intermediate file D2.

Thus, the printer 20 can acquire the printing jobs D7, D8 and effectprinting.

In this embodiment, an intermediate file is generated from printing dataso that another program can be executed during the execution of printingby the printer 20, but RGB bit map data may be generated directly fromprinting data without providing the intermediate file preparing module.

Further, in monochromatic image printing, if monochromatic bit map datais the only printing data, the printing job generating module need notbe provided with the function for conversion to monochromatic bit mapdata.

(3) Color-reproducible Color Region in Monochromatic Image Printing

FIG. 6 shows an example of changes in brightness relative to the amountof ink ejected per unit area when color inks are ejected eachindependently onto a white printing paper, in which the amount of inkejected (unit: %) is plotted along the axis of abscissa and brightnessL* is plotted along the axis of ordinate (L* is 0 to 100%, the larger,the brighter). The amount of ink ejected corresponds to the ratio of thenumber of dots ejected relative to the total number of dots per unitarea on the printing paper, in other words, the density of dots relativeto the printing paper. Brightness change curves differ depending oncomponents even in the case of inks of the same color and also differdepending on the type of printing paper to be printed.

When the amount of ink ejected is 0%, that is, when no color ink isejected, the brightness represents the brightness of the printing paperitself, but assumes a value somewhat smaller than 100%. When the colorink K is ejected 100%, that is, when it is ejected all dots per unitarea relative to the printing paper, the brightness becomes the lowest,but assumes a value somewhat larger than 0%. The brightness L* of eachcolor ink lowers according to the amount of ink ejected while describinga downwardly expanded curve.

As to the color inks C, M, and Y high in saturation, C and M exhibitsimilar changes in brightness and Y is higher in brightness than C andM. The color inks c and m low in saturation exhibit similar changes inbrightness and their brightnesses lie between the brightnesses of C andM and the brightness of Y. The color ink k1 which is a light black colorink exhibits a change in brightness close to that of the color inks Cand M. Likewise, the color ink k2 which is a light black color inkexhibits a change in brightness close to that of the color inks c and m.The densities of the color inks k1 and k2 may be set to various values.For example, the density of k2 may be set so as to exhibit a change inbrightness close to that of C and M or close to that of Y.

In FIG. 7, a color region (GAMUT) capable of being color-reproducedusing plural color inks having the above properties is shownschematically in a projected state onto an a*L* plane in an L*a*b* spacewhich is an absolute color space. FIG. 8 illustrates this color regionschematically in a projected state onto an a*b* plane. L* provided onthe vertical axis in FIG. 7 represents the above brightness, while a*and b* (unit: %) in FIGS. 7 and 8 represent hue and saturation.Saturation is represented in terms of a distance from the center (theposition of K) in FIG. 8, while hue is represented in terms of adirection from the center in the same figure. The color region in colorprinting is indicated with a solid line, while the color region inmonochromatic image printing is indicated with a dotted line. That thecolor region is represented by L*a*b* is a mere example and it may berepresented by CIExy chromaticity diagram for example.

Although in this embodiment there are used cyan and magenta color inksC, M low in both saturation and density, it is not always necessary inpracticing the invention that cyan and magenta color inks be low indensity insofar as they are low in saturation. Even in case of printinga monochromatic image using such cyan and magenta color inks, the colorregion which is color-reproduced falls under such regions as indicatedwith dotted lines in FIGS. 7 and 8.

As to a* shown in the figures, the stronger the magenta, the larger thevalue thereof, and the stronger the green, the smaller the valuethereof, while as to b*, the stronger the yellow, the larger the valuethereof, and the stronger the blue, the smaller the value thereof.Therefore, among the chromatic color inks high in saturation, Crepresents coordinates which are minus in both a* and b*, M representscoordinates close to +100 in a* axis direction, and Y representscoordinates close to +100 in b* axis direction. The chromatic inks c andm low in saturation assume positions closer to L* axis rather than C andM. According to an actual measurement, the positions of c and m in FIG.8 are deviated from straight lines connecting the center with thepositions of C and M. The achromatic color ink K high in densityrepresents coordinates close to 0 on L* axis. The achromatic color inksk1 and k2 low in density represent coordinates which become larger in L*in this order on L* axis.

In color printing, a color region S1 capable of being color-reproducedis a space surrounded with C, M, Y, K and coordinates W of the printingpaper itself. Color-reproducible color regions substantially in cyan andmagenta directions in color printing are indicated with solid linearrows in the figures. On the other hand, in printing a monochromaticimage, since C and M are not used, a color-reproducible color region S2corresponds to a space surrounded with c, m, Y, K and coordinates W ofthe printing paper itself. That is, in monochromatic image printing,solid line arrows in both C and M directions in the figures project fromthe color region S2 and thus the color-reproducible color region isnarrowed substantially in cyan and magenta directions and is notnarrowed substantially in the direction of yellow.

LUTs 2 and 3 for monochromatic image printing are tables in which RGBbit map data are correlated with color data of 256 gray scales withrespect to each of K, k1, k2, Y, c, and m. That is, in thecolor-reproducible color region S2 which has been narrowed substantiallyin cyan and magenta directions there is made color reproduction using256 gray scales. Since in color printing there is made colorreproduction using 256 gray scales in the color-reproducible colorregion S1 which is not narrowed, color reproduction can be done inmonochromatic image printing while enhancing the gradationcharacteristic substantially in cyan and magenta directions. In otherwords, resolution substantially in cyan and magenta directions isimproved. That is, the color tone of a monochromatic image printed canbe adjusted minutely with respect to cyan and magenta color components.

Further, since the color ink Y high in saturation is used inmonochromatic image printing, the color-reproducible color region S2 iswide substantially in the direction of yellow.

When looking at a monochromatic image, the human eye senses yellowcomponent relatively small in comparison with cyan and magentacomponents. Therefore, even with use of the color ink Y high insaturation, it is possible to develop a color tone of a fine texture inappearance. On the other hand, as shown in FIG. 8, since the distancefrom the center up to Y is the same as in color printing, it is possibleto ensure a sufficient selection range of saturation substantially inthe direction of yellow. As a result, in comparison with the case ofprinting a monochromatic image with separate use of cyan, magenta andyellow color inks all low in saturation, it is possible to obtain asufficient power of expression while developing a color tone of a finetexture in appearance. Moreover, since monochromatic image printing canbe conducted using low-saturation color inks c and m which are used in asix-color printable printer, it is no longer required to separatelyprovide special color inks.

In monochromatic image printing with sepia color imparted to neutralgray, a small amount of c and a large amount of Y can be used, so thatsepia color can be expressed to a more satisfactory extent than beforein comparison with the case of using a yellow color ink low insaturation.

Further, since the color inks C and M high in both saturation anddensity are not used in monochromatic image printing, what is calledcolor twist does not occur. FIG. 9 is a schematic diagram wherein dotsformed on printing paper are compared between the use of C and M high inboth saturation and density and the use of c and m low in bothsaturation and density. In monochromatic image printing, dots of c and mare mixed in dots of K, k1, and k2. The ratio between the number of dotsin the use of C and M high in both saturation and density and the numberof dots in the use of c and m low in both saturation and density may bechanged according to properties of color inks and the ratios of dotnumber shown in the figure is merely one example.

In monochromatic image printing, the ratio of chromatic color inks toBlack color inks is small in many cases. In there are used C and M highin both saturation and density, dots formed are very sparse, as shown inthe upper portion of the figure. Consequently, an apparent hue does notbecome uniform, so that there may occur a case where an unintended huecalled color twist appears. On the other hand, if there are used c and mlow in both saturation and density, the density of dots formedincreases, as shown in the lower portion of the figure. As a result, anapparent hue becomes uniform and there does not appear any unintendedhue.

In monochromatic image printing, three kinds of Black color inks K, k1,and k2 different in density are used and color reproduction is performedwhile selecting an appropriate Black color ink or inks according to thebrightness of a monochromatic image. FIG. 10 shows the amounts of colorinks K, k1, k2, Y, c, and m used in terms of gradation values relativeto the brightness of the monochromatic image with saturation assumed tobe zero (achromatic 256-gray scale bit map data).

Actually, in printing sepia color for example, a hue is created usingthe color inks c, m, and Y. In actual processing, RGB bit map data areconverted to color data of K, k1, k2, Y, c, and m with use of such a LUTas affords the illustrated relation.

As shown in the figure, chromatic color inks c, m, Y are used in a highbrightness portion, while Black color inks are used in a low brightnessportion. Printing is performed using one or a combination of pluralBlack color inks. Since Black color inks comprise the color inks K, k1,and k2 different in density, it is possible to select an appropriateBlack color ink according to the brightness of image. Further, by usinglight black color inks k1 and k2, it is possible to diminish the gap inbrightness at the time of replacing various chromatic color inks withBlack color inks.

The amounts of inks shown in FIG. 10 are based on the use of LUT2 withpriority given to high image quality in monochromatic image printing.When using LUT3 with priority given to running cost, the curves whichrepresent the amounts of color inks K, k1, and k2 used shift in a higherbrightness direction, as shown in FIG. 11. As a result, the amounts ofchromatic color inks c, m, and Y decrease. That is, by switching LUTs 2and 3 from one to the other, it is possible to change the ratio betweenplural Black color inks and other color inks.

(4) Operation of the Printing System

The operation of the printing system 100 constructed as above will bedescribed below with reference to an example of display screen.

FIGS. 12 to 14 are flowcharts showing an outline of processingsperformed by the personal computer 10 in the printing system 100. It isassumed that before execution of the illustrated processing flow, inkcartridges of C and M are loaded as ink cartridges 28 b and 28 c tocartridge holders 28 in color printing and ink cartridges of k1 and k2are loaded as ink cartridges 28 b and 28 c in monochromatic imageprinting, both by a user.

APL has a printing function for APL. When a print execution menu to bedisplayed on the display 17 a is selected by the printing function forAPL, the printer driver causes the print setting acquiring module m4 tooperate under control of the function control module and performs aprocessing for displaying a print interface main screen (not shown)(step S105). In the same screen there are displayed only suchinformation pieces as can cope with ordinary print instructions, e.g.,paper type selecting region, printing page range indicating region,print type setting button, print button, and cancel button. That is,with the mouse 16 b for example, the user can select and input the typeof printing paper in the paper type selecting region, and can set andinput printing start page and end page in the printing page rangeindicating area. Various print parameters are acquired from operationinputs to those regions (step S110).

Next, the processing is branched according to a mouse operation to abutton provided on the screen (step S115).

If the print type setting button is clicked by the mouse 16 b, theprocessing flow advances to step S120 and there is displayed a printtype setting screen 200 shown in FIG. 15. On the left-hand side of thescreen 200 are displayed a print type selecting field 201, OK button205, and Cancel button 206. In the print type selecting field 201, onlyeither “Color” or Monochromatic Image can be selected and inputted bythe mouse 16 b. Below the “Monochromatic Image” there is displayed anink ratio selecting field 202, whereby when “Monochromatic Image” isselected and inputted, there can be selected and inputted only either“Priority given to High Image Quality” or “Priority given to RunningCost. When “Priority given to High Image Quality” is selected andinputted, the ratios of color inks are set so as to give such amounts ofinks used as shown in FIG. 10, while when “Priority given to RunningCost” is selected, the ratios of color inks are set so as to give suchamounts of inks used as shown in FIG. 11.

When “Monochromatic Image” is selected and inputted, a hue setting field203 and an application quantity setting field 204 are displayed on theright-hand side of the print type setting screen 200. In the hue settingfield 203 are displayed a hue ring 203 a including cyan, magenta, andyellow (C, M, and Y, respectively, in the figure) and a needle 203 bwhich can rotate with the center of the hue ring 203 a as a rotationalcenter. With the mouse 16 b, the needle 203 b can be positioned to adesired hue on the hue ring 203 a. The positions of “Sepia,” “Warm,” and“Cool” are shown in the hue setting field 203, so that the needle 203 bcan be set to those positions easily.

In the application quantity setting field 204 are displayed a lineargroove 204 a and an arrow 204 b which can slide along the groove 204 a.When the arrow 204 b is moved to the leftmost position by the mouse 16b, a black-and-white image with no hue applied thereto is set, while asthe arrow 204 b is moved rightwards, there is set a monochromatic imagein such a manner that the hue set in the hue setting field 203 becomesstronger.

When an OK button 205 is clicked, the print type which has been selectedand inputted in the print type selecting field 201 is obtained, and if“Monochromatic Image” is selected and inputted, there are obtained anink ratio setting selected and inputted in the ink ratio selecting field202, a hue corresponding to the position of the needle 203 b in the huesetting field, and an application quantity corresponding to the positionof the arrow 204 b in the application quantity setting field (stepS125). Then, the print type setting screen 200 is erased and theprocessing flow returns to step S105, in which the print interface mainscreen is again displayed. Though not shown in the processing flow, if aCancel button 206 is clicked, the information inputted by operation isdestroyed, the print type setting screen 200 is erased, and theprocessing flow returns to step S105.

That is, the processings of steps S120 to S125 not only constitute aprint type acquiring means which acquires a print type of eithermonochromatic image printing or color printing, but also constitute aratio setting acquiring means which acquires a ratio setting betweenplural Black color inks and other color inks.

If the cancel button on the print interface main screen is clicked atstep S115, the processing flow advances to step S130, which cancels thethus obtained print parameters and end this processing flow.

If the Print button on the print interface main screen is clicked, theprocessing flow advances to step S135, in which the print data acquiringmodule ml is operated to acquire print data D1 generated by APL throughGDI. Next, the intermediate file generating module m2 is operated togenerate an intermediate file on the basis of the acquired print data,which file is stored in the hard disc 14 a temporarily (step S140).

Thereafter, the print job generating module m3 is operated, causing theprocessing flow to branch according to the set print type (step S145).If “Color” is selected and inputted in the print type selecting field201, the processing flow advances to step S205 in FIG. 13, while if“monochromatic image” is selected and inputted in the print typeselecting field 201, the processing flow advances to step S305 in FIG.14.

In step S205, the intermediate file D2 is read and RGB bit mapconversion is performed on the basis of the intermediate languageincluded in the intermediate file D2 to generate RGB bit map data D3 onRAM 13.

In the printing system 100, as ink cartridges 28 b and 28 c inmonochromatic image printing, ink cartridges of k1 and k2 are loadedinstead of ink cartridges of C and M, so there may occur a case whereink cartridges of C and M are not loaded despite the processing beingcarried out is for color printing. To avoid this inconvenience, there ismade a processing for acquiring from the printer 20 color inkinformation which includes such information pieces as ink colors andresidual amounts in the loaded ink cartridges and for checking whetherall of the color inks necessary for printing are employable or not.

In step S210, the above color ink information is acquired from theprinter 20. More specifically, when a request for acquiring color inkinformation is outputted from the personal computer 10 to the printer 20through the printer I/F 19, the printer 20 acquires this request,generates color ink information from information indicating ink colorand residual amount in each of ink cartridges, and outputs the generatedinformation to the personal computer 10 through communication I/O 26. Inthis way the personal computer 10 can acquire the color ink informationoutputted from the printer 20.

Next, on the basis of the color ink information there is made judgmentas to whether color printing can be executed or not (step S215). Thatis, when all of the ink colors K, c, m, C, M, and Y are included in thecolor ink information and when the residual amounts of inks in all theirink cartridges are not zero, it is judged that printing can be done.Therefore, for example when ink cartridges of k1 and k2 are loaded asthe ink cartridges 28 b and 28 c, it follows that C and M are notincluded as ink colors in the color ink information, so the conditionsfor printing are not satisfied.

If the conditions for printing are met in step S215, the processing flowadvances to step S225, while if the answer is negative, the flow shiftsto step S220. In step S220 there is made indication on an error displayscreen to the effect that printing cannot be done and that inkcartridges necessary for color printing should be loaded. Then, afterthe necessary ink cartridges have been loaded and OK button on thescreen is clicked, there are again conducted the processings of stepsS210 to S215. In step S220, this processing flow may be ended afterdisplay of the error display screen.

In step S225 there is performed a color data conversion processing forcolor printing. More specifically, RGB bit map data D3 is converted tocolor data DS which comprises six kinds of K, C, M, Y, c, and m. Thisprocessing is carried out by converting 256-gray scale bit map data ofeach of R, G, B into 256-gray scale color data of each of K, C, M, Y, c,and m with reference to the foregoing LUT1 for color printing.

The color data D5 is binarized and a printing job D7 corresponding to K,C, M, Y, c, and m is generated and transmitted to the printer 20 (stepS230). This processing flow is now ended. Then, the printer 20 acquiresthe printing job D7 and drives the print head 30 on the basis of theprinting job D7 for form dots of color inks, thereby performing colorprinting.

When “Monochromatic Image” is selected and inputted in the print typeselecting field 201, the processing flow advances from step S145 in FIG.12 to step S305 in FIG. 14, in which the intermediate file D2 is readand is converted to achromatic bit map data on the basis of theintermediate language included in the intermediate file D2.

The printing data D1 acquired may be data of an image not containinginformation on hue or may be data for a color image. In the latter case,since gradation data on the colors R, G, and B are included, theprocessing to be carried out is to convert the gradation data intobrightness data to afford achromatic bit map data. For example, if thegradation data on R, G, and B are represented by R, G, and B,respectively, brightness data L can roughly be calculated by thefollowing arithmetic expression (1):

L=0.30×R+0.59×G+0.11×B   (1)

Of course, the brightness data in question can be obtained by variousother methods. For example, gradation data may be averaged or added toobtain brightness data. In the case where the printing data Dl includessuch separated brightness data as data expressed in L*a*b* form, theprocessing for conversion to brightness data may be omitted.

Next, the achromatic bit map data is converted to RGB bit map data withhue not applied thereto and a hue is applied thereto on the basis ofboth hue and amount thereof to be applied which have been acquired fromthe hue setting field 203 and application quantity setting field 204,thereby making conversion into RGB bit map data D4 with hue appliedthereto (step S310). The RGB bit map data D4 is generated on RAM 13.Components (R0, G0, B0) of R, G, B included in the RGB bit map data withhue not applied thereto can be obtained from the brightness data L inaccordance with a predetermined conversion expression. Given thatcomponents of R, G, and B in the acquired hue to be applied are (r, g,b), a mean value of r, g, b is a, and the acquired application quantityis A0 (0≦A0≦1), the components (R, G, B) of R, G, B in the hued RGB bitmap data D4 can be calculated, for example, in accordance with thefollowing arithmetic expressions (2) to (4):

R=R0−a×A0+r×A0   (2)

G=G0−a×A0+g×A0   (3)

B=B0−a×A0+b×A0   (4)

Of course, any other method than the use of the above expressions may beused for the conversion of achromatic bit map data into RGB bit mapdata.

Thereafter, the foregoing color ink information is acquired from theprinter 20 (step S315). Next, from the color ink information it isjudged whether it is possible to effect monochromatic image printing(step S320). More specifically, if all of K, k1, k2, C, M, and Y areincluded as ink colors in the color ink information and if all theirresidual amounts are not zero, there is made judgment that it ispossible to effect printing. Therefore, if ink cartridges of C and M areloaded as ink cartridges 28 ba and 28 c, the conditions for printing arenot satisfied.

If the answer is affirmative in step S320, the processing flow advancesto step S330, while if the answer in step S320 is negative, the flowshifts to step S325. In step S325, the same error display screen as instep S220 is displayed. After the required ink cartridges are loaded andOK button provided on the screen is clicked, the processings of stepsS315 to S320 are again performed.

Instep S330, the processing flow is branched in accordance with thesetting of ink ratio which has been set. If “Priority given to HighImage Quality” is selected and inputted in the ink ratio selecting field202, the processing flow advances to step S335, in which there isperformed a color data conversion processing for priority given to highimage quality in monochromatic image printing. To be more specific,there is conducted a processing for converting 256-gray scale bit mapdata on each of R, G, B into 256-gray scale color data D6 on each of K,k1, k2, Y, c, and m with reference to the foregoing LUT2. The LUT2 is acolor conversion table for priority given to high image quality inmonochromatic image printing. The values of color data of Y, c, m out ofthe data which constitute the color data D6 become larger than in theuse of LUT3.

Thereafter, the color data D6 is binarized and a printing job D8corresponding to K, k1, k2, Y, c, and m is generated and transmitted tothe printer 20 (step S340). Now this processing flow is ended. Theprinter 20 receives the printing job D8 and actuates the print head 30on the basis of the printing job D8 to form dots of the color inks K,k1, k2, Y, c, m, thereby printing a monochromatic image.

On the other hand, if “Priority given to High Image Quality” is selectedand inputted in the ink ratio selecting field 202, the processing flowadvances from step S330 to step S345, in which there is performed acolor data conversion processing for priority given to running cost inmonochromatic image printing. More specifically, there is performed aprocessing for converting 256-gray scale bit map data on each of R, G, Binto 256-gray scale color data D6 on each of K, k1, k2, Y, c, m withreference the foregoing LUT3. The LUT 3 is a color conversion table forpriority given to running cost in monochromatic image printing. Thevalues of color data of K, k1, k2 out of the data which constitute thecolor data D6 become larger than in the use of LUT2.

Subsequently, as in step S340, the color data D6 is binarized and aprinting job D8 corresponding to K, k1, k2, Y, c, m is generated andtransmitted to the printer 20 (step S350). Now this processing flow isended. On this basis of the printing job D8 the printer 20 forms dots ofthe color inks K, k1, k2, Y, c, m and thereby print a monochromaticimage.

Thus, with the personal computer 10 which carries out the processings inaccordance with the flow of FIGS. 12 to 14 and the printer 20 connectedthereto, color reproduction is effected under an enhanced gradationcharacteristic within a color-reproducible color region while the samecolor region is narrowed by c and m low in saturation, Y of a highsaturation, and K, k1 and k2 which are Black color inks. In other words,in the printing system 100, Y of a high saturation is used together withK, k1 and k2 as achromatic inks and c and m low in saturation andmonochromatic image printing is performed while the color region is notnarrowed substantially in the direction of yellow from the time of colorprinting. As a result, it becomes possible to print a monochromaticimage of a high image quality having a sufficient power of expressionwhile ensuring a sufficient selection width of saturation.

Besides, the user can set which of monochromatic image printing andcolor printing is to be performed, and even if the number of loadableink cartridges is limited, both monochromatic image printing and colorprinting can be done in the same printing sys tem 100. Thus, theprinting system 100 is convenient. Although the color inks k1 and k2 aslight black color inks are provided so that they can be replaced withthe color inks C and M high in saturation, it is possible to preventsuch printing as is performed using unintended color inks, becauseprinting is performed after making sure that the color inks to be usedare required color inks.

Further, it is possible to set an ink ratio as to whether priorityshould be given to high image quality or to running cost inmonochromatic image printing. Also in this point the printing system 100is convenient.

In the above embodiment, means for inputting first, achromatic,multi-gradation image data is implemented in steps S135, S140, and S305.At this time, in step S305, a chromatic color image data is inputted,brightnesses of picture elements are determined on the basis of theinputted image data and are used as the above first image data.

Means for acquiring hue is implemented in steps S105 and S110. But insteps S105 and S110 there also is obtained an application quantityindicative of strength to be applied in addition of hue.

Further, means for converting the above first image data to the abovesecond image data is implemented by steps S205 and S335 or S345. At thistime, the above first image data is converted to third image data withhue applied to the first image data, followed by conversion to the abovesecond image data. That is, the former conversion is a processing forchanging the intensity of hue which is applied correspondingly to theapplication quantity acquired and is implemented by step S205.

Then, by utilizing a color conversion table, the third image data issubjected to color conversion to the second image data. This conversionis implemented by step S335 or S345. The color conversion table utilizedat this time corresponds to the range of a color-reproducible colorregion which is determined by a saturation capable of being reproducedby the foregoing cyan color ink, a saturation capable of beingreproduced by the foregoing magenta color ink, and a saturation capableof being reproduced by the foregoing yellow color ink. That is, a colorspace after the conversion by the color conversion table corresponds tothe range of the color region referred to above. Although the abovethird image data has a hue, the number of color data capable of beingobtained is within the range of the maximum gradation number of thefirst image data. Thus, on the basis of gradation value of the firstimage data it is possible to make conversion to the second image data ofmulti-gradation with the acquired hue applied thereto.

As to the color conversion table, plural Black color inks different indensity are premised and plural such color conversion tables areprovided so as to give different amounts of the Black color inks used.Such plural color conversion tables correspond respectively toconversion processings for priority given to high image quality and forpriority given to running cost. Further, means for acquiring a selectionresult corresponding to changes in the amounts of the Black color inksused is implemented by steps S105 and S110. Moreover, the processingwhich selects any of the color conversion tables on the basis of theselection result and which causes color conversion to be effected usingthe selected color conversion table is implemented by step 330.

Further, means for converting the above second image data to theforegoing printing data of low gradation is implemented as a color databinarizing processing in steps S340 and S350.

(5) Modifications

The printing system according to the present invention may beimplemented in various constructions.

For example, the printer may be integral with the computer, or may be adedicated printer for printing only monochromatic images. It is notalways necessary to have both color inks c and m. Having only one of thecolor inks c and m will do. Also in this case, monochromatic imageprinting can be done without narrowing the color region substantially inthe direction of yellow from the time of color printing and it ispossible to print a monochromatic image of a high image quality having asufficient power of expression while ensuring a sufficient selectionrange of saturation. Moreover, the printer is not limited to the printerusing piezoelectric elements for the ejection of color inks to formdots. For example, there may be used a bubble type printer whereinbubbles are generated within ink passages and color inks are ejectedthereby. There also may be used a printer wherein the size of dotsformed is variable, such as what is called a variable printer.

Further, plural color inks may be filled into a single ink cartridge. Inthe case where color printing and monochromatic image printing areperformed while being switched from one to the other, there areprovided, for example, an ink cartridge for color printing filled withall of the color inks K, C, M, Y, c, m and an ink cartridge formonochromatic image printing filled with all of the color inks K, k1,k2, Y, c, m and the two ink cartridges are replaced one with the other.

Providing ink cartridges replaceably is merely one example ofconstruction. For example, there maybe adopted a construction whereinall ink cartridges of K, k1, k2, C, M, Y, c, and m are loaded to theprinter and, in color printing, color reproduction is performed usingthe color inks K, C, M, Y, c, and m, while in monochromatic imageprinting, color reproduction is performed using the color inks K, k1,k2, Y, c, and m. Of course, the color inks k1 or k2 may be providedreplaceably with only the color ink C or with only the color ink M. Incase of using five kinds of colors K, k1, Y, c, and m without using thecolor ink k2 in monochromatic image printing, the color ink k1 may beprovided replaceably with the color ink C or M.

Further, as to the processing flow shown in FIGS. 12 to 14, theexecution of the processings is not limited to within the personalcomputer, but a part or the whole thereof may be executed by the printeror using a dedicated image processor.

In the above embodiment the printer driver applies a hue to anachromatic image so as to give a desired tone in monochromatic imageprinting, but for generating printing data on a monochromatic image withhue applied thereto by APL, the foregoing steps S305 to S310 maybesubstituted by a processing which involves making RGB bit map conversiondirectly from an intermediate file to generate RGB bit map data. Also inthis case, by step S315 and subsequent processings, if colorreproduction is performed under an enhanced gradation characteristic ina color-reproducible color region while narrowing the same color regionusing c and m low in saturation, Y of a high saturation, and K, k1, andk2 which are Black color inks, it is possible to print a monochromaticimage of a high quality having a sufficient power of expression whileensuring a sufficient selection range of saturation.

The processing to be performed in case of applying a hue so as to give adesired hue is not limited to the processing wherein there is madeconversion to such color data as K, Y, c, and m after generation of RGBbit map data with the hue applied thereto. There may be conducted aprocessing such that the color data of Y, c, and m are corrected for theapplication of hue after conversion from unhued, achromatic bit map datato such color data as K, Y, c, and m.

Further, at the time of generating color data for priority given to highimage quality and color data for priority given to running cost inmonochromatic image printing, the processing for generating the colordata is not limited to the processing that uses different LUTs. Thecolor data may be generated by an arithmetic processing for conversionfrom one color data to the other color data. For example, in case ofconverting the color data for priority given to high image quality tothe color data for priority given to running cost, there may beconducted an arithmetic processing which converts a portion of the colordata Y, c, and m into color data of an achromatic color ink such as k2.

For example, this arithmetic processing can be done in the followingmanner. First, C and M color data conversion values are calculated fromthe color data of c and m and minimum values MIN of the color data of C,M, and Y are determined. Next, given that gradation values of k2, Y, c,and m are k2, Y, c, and m, respectively, gradation values of k2, Y, c,and m after conversion are k2′, Y, c′ , and m′ , respectively, andcorrection coefficients are A1 to A4, the gradation data afterconversion can be obtained in accordance with the following arithmeticexpressions (5) to (8):

k2′=k2+A1×MIN   (5)

Y′=Y−A2×MIN   (6)

c′=c−A3×MIN   (7)

m′=m−A4×MIN   (8)

The correction coefficients A1 to A4 may be determined according todensities of the color inks k2, Y, c, and m.

Thus, the conversion to color data for priority given to running costcan be done without using the LUT for that priority.

According to the present invention, as set forth above, it is possibleto provide a printing system which, in any of various modes, can print amonochromatic image of a high image quality having a sufficient power ofexpression while ensuring a sufficient selection range of saturation.The printing system is also applicable as a printing method and programfor the system, as well as a medium which stores the program.

The foregoing invention has been described in terms of preferredembodiments. However, those skilled, in the art will recognize that manyvariations of such embodiments exist. Such variations are intended to bewithin the scope of the present invention and the appended claims.

1. A color ink set for monochromatic image printing, said color ink setcomprising: a plurality of black inks each different in brightness; aplurality of cyan color inks each different in brightness; a pluralityof magenta color inks each different in brightness; and a yellow colorink; wherein a brightness of the yellow color ink is higher than abrightness of a cyan color ink having the highest brightness out of theplurality of cyan color inks, and the brightness of the yellow color inkis higher than a brightness of a magenta color ink having the highestbrightness out of the plurality of magenta color inks.